1. Field of the Invention
The present invention relates to an image forming device, and more particularly, to an image forming device which projects light emitted from a light source onto a predetermined area of a photosensitive medium, thereby improving an image transfer efficiency and removing a remaining electrostatic latent image.
2. Description of the Related Art
Image forming devices such as photocopiers, printers, facsimile machines, and multi-function machines are used to print images. Among these devices, printers are most frequently used to reproduce computer-processed information.
FIG. 1 is a schematic view showing a conventional image forming device.
Referring to FIG. 1, an image forming device includes a charging unit 10, an organic photoconductive drum 20, a light exposure unit 30, a developing unit 40, a transfer roller 50, a pre-transfer lamp 60, and a latent image removing lamp 70.
A charging roller 10a is electrically charged by a voltage and is rotated to electrically charge a photosensitive medium coated along an external circumference of the organic photoconductive drum 20. Then, an electrostatic latent image is formed on the organic photoconductive drum 20 exposed to light emitted from the light exposure unit 30. Next, the developing unit 40 develops the electrostatic latent image formed on the organic photoconductive drum 20 by using a developer.
The transfer roller 50 transfers an image formed by the developing unit 40 to a recording paper (not shown). The image forming device fuses the image printed on the recording paper by using a fusing unit (not shown) and discharges the paper.
Meanwhile, the pre-transfer lamp 60 is positioned at a position to project the light onto an area of the organic photoconductive drum 20 that corresponds to the area between the developing unit 40 and the transfer roller 50. The pre-transfer lamp 60 projects the light to the developer coated on the surface of the organic photoconductive drum 20 to thereby increase an electric potential of the developer. Accordingly, a binding force of the developer decreases and thus image transfer efficiency is improved. At this time, the light emitted from the pre-transfer lamp 60 is focused on the organic photoconductive drum 20 by a lens 62 which corresponds to the pre-transfer lamp 60.
The pre-transfer lamp 60 may be disposed to project the light onto a backside of the recording paper (not shown). At this point, since the transmissivity of the light varies depending on features of the recording paper, there may be a variation in the transfer efficiency. In consideration of this fact, the pre-transfer lamp 60 may be disposed at a position A to project the light directly onto the surface of the organic photoconductive drum 20 in the same direction as the dotted line of FIG. 1.
Meanwhile, in order to form a new electrostatic latent image on the organic photoconductive drum 20, it is necessary to remove the remaining latent image (a remaining electric potential) that still remains after passing through the transfer roller 50. The latent image removing lamp 70 projects light onto the area of the organic photoconductive drum 20 that has already passed the transfer roller 50 to remove the remaining latent image.
As described above, such a conventional image forming device must separate the pre-transfer lamp 60 and the latent image removing lamp 70 to maintain transfer efficiency and remove the remaining latent image to improve the image quality.
FIG. 2 is a view showing the arrangements of the pre-transfer lamp 60 and the latent image removing lamp 70.
Referring to FIG. 2, the pre-transfer lamp 60 and the latent image removing lamp 70 are structured so that a plurality of LED emitting elements are arranged on a separate PCB base plate in a predetermined pattern, and provided with a power via a separate power cable 90.
That is, the conventional image forming device must include separate light emitting elements to project the light to the organic photoconductive drum 20, thereby improving the transfer efficiency and the image quality. The light emitting elements require a separate base-plate to be arranged thereon and the separate power cable 90 to supply the power therethrough. Accordingly, there are problems due to complicated structure and increased cost.